Absolute location of lanthanide energy levels and the performance of phosphors

Methods to construct the absolute position of the energy levels of divalent and trivalent lanthanides with respect to the valence band and conduction band of a host compound are available and can be applied to many different compounds. With the diagrams of lanthanide levels in SrAl2O4, LiYSiO4, and CaGa2S4 it will be demonstrated how they can be used to understand phosphor performance. The quenching of Ce3+ and Eu2+ 5d–4f luminescence, the electron and hole trapping ability of the lanthanides, and the valence stability of lanthanide ions are discussed.